ATS Transfer Switch Panels
ATS transfer switch panel: starts the generator when the mains fails and switches back when it returns. ATS sizing to generator power and installation.
The ATS (automatic transfer switch) panel, installed between the generator and the mains, allows the generator to come online automatically, without manual intervention, when the mains fails.
How does it work?
- The ATS continuously monitors mains voltage and frequency.
- If the mains fails or goes outside its limits, the ATS sends a start command to the generator.
- Once the generator’s voltage and frequency have stabilised, it transfers the load to the generator.
- When the mains returns and has stabilised, it transfers the load back to the mains.
- The generator runs off-load for its cool-down period and then stops.
Mechanical and electrical interlocking, which prevents the mains and the generator from being connected to the load at the same time, is the foundation of the system’s safety.
How do you choose the right ATS?
- Current: In a 400 V three-phase system, the generator current is calculated approximately as kVA × 1.44, and the next standard ATS rating up is selected.
- Number of poles: A 3-pole or 4-pole ATS is used depending on whether the neutral needs to be switched.
- Control: A control unit that works in harmony with the generator control panel and has adjustable time delays is preferred.
- Location: The panel is placed close to the main distribution board, in a location accessible to authorised personnel.
ATS with Terex Diesel
We select ATS panels to match the generator’s power, then test and commission them together with the generator. For projects where several generators will run together, take a look at our synchronization panel solutions.
For the right ATS for your needs, contact us.
ATS connection diagram
- Mains fails, or voltage/frequency goes out of limits.
- The ATS waits a few seconds (to ride through brief dips), then sends a start signal to the generator.
- Once the generator reaches voltage and frequency, the ATS transfers the load; typically 10–15 seconds in total.
- When mains returns, the ATS confirms it is stable, transfers the load back, and the generator stops after a cool-down run.
Frequently asked questions
What does an ATS panel do?
An ATS (automatic transfer switch) continuously monitors the mains. When the power goes out, it sends a start command to the generator and transfers the load to the generator once it is ready; when the mains returns, it transfers the load back to the mains and stops the generator after a cool-down period.
What amp rating should an ATS have?
The ATS is selected according to the generator's rated current. In a 400 V three-phase system, the current is found approximately with the formula kVA × 1.44; for example, a 155 kVA generator draws about 223 A, so the next standard rating up, a 250 A ATS, is selected.
Does the ATS come with the generator?
The ATS panel is a separate option, supplied with the set on customer request. It can be factory-tested and shipped together with the generator, or added to an existing installation later.